Theoretical Investigation of Metallic Phase of the Group V Crystals under Pressure.

在局域密度泛函形式下，利用赝势守恒范数，计算了磷(P)的斜方A7相和简单立方(Sc)相，砷(As)和锑(Sb)的Sc相和体心(BCC)相的总能量。P的计算结果成功地解释了压力作用下从A7相到Sc相的相变。计算的金属Sc相的电子结构表明，该相中的成键具有可观的共价性。研究还发现，SC结构在压力作用下的稳定性是由于静电能量对压缩的贡献。此外，P原子核心d轨道的缺失对于解释P与其它5B元素在加压相变中的不同是非常重要的。SC-AS和BCC-Sb的计算状态方程与实验符合得很好。为了了解这两种元素相变的差异，还计算了假设赝势的总能量，这些赝势的构造使得As和Sb的赝势之间有一个S(或p)能级。结果表明，这种差异主要是由p能级引起的。

The total energies of the rhombohedral A7 and the simple cubic (SC) phase for phosphorus (P), and those of the SC and the body centered (BCC) phase for arsenic (As) and antimony (Sb) are calculated within the local-density functional formalism by using the norm conserving pseudopotentials.1. The calculated results for P succesfully explain the phase transition from the A7 to the SC phase under pressure. The calculated electronicstructure of the metallic SC phase reveals that the bonding in this phase has an appreciable amount of covalency. It is also found that the stabilization of the SC structure under pressure is due to the fact that the cotribution of the electrostatic energy to the compression. Moreover, it is shown that the absence of the core d-orbitals of a P atom is very important in explaining thdifference between P and other 5B elements in the phase transition under pressure.2. Calculated equations of state for the SC-As and the BCC-Sb are in exellent agreement with the experimental ones. In order to see the difference between the phase transitions for both elements, the total energies are also calculted for hypothetical pseudopotentials, which are so constructed as to have an s (or p) level between As's and Sb's one. It is shown that the difference is mainly due to the p level.